Process for enhancing the octane number of catalytically cracked naphtha fractions



May 3, 1960 PRIMARY F RACEONATOR PROCESS FOR EN G. ANNABLE ETAL HANGINGTHE OCTANE NUMBER OF CATALYTICALLY CRACKED NAPHTHA FRACTIONS CATALYTICCRACKING UNIT Filed NOV. 5, 1956 I4 GAS SECONDARY FRACTIONATOR w L HEAVYGAS on.

, HYDROGENATING UNIT :7

2o 1 22 PRODUCT REFORMING UNIT mmvroxs WELDON G. ANNABLE WILLIAM L.JACOBS ATTORNEY I I 2,935,460 iiRocE'ss FOR ENHANCING THE OCTANE NUM-BER F CATALYTICALLY CRACKED NAPHTHA FRACTIONS Weldon G. Annable,Mundelein, and William L. Jacobs,

Crystal Lake, ilL, assigno'rs to The Pure Oil Company,

Chicago, 111., a corporation of Ohio Application November 5, 1956,Serial No.6 2 0,416

' 5 Claims. (Cl. 208-76) i This invention relates to the productionoff-high octane number gasolines. It is more specifically concerned withimproving the sensitivity of a gasoline produced in a catalytic crackingprocess. o

In order to afford a more realistic expression of the road performancecharacteristics'of gasoline-type motor fuels, a sensitivity factor isemployed as a criterion. Sensitivity is defined as the differencebetween the Fl or research octane number (CRC designation F-1545) andthe F-2 or motor octane number (CRC designation F--2545), asconventionally obtained.- ,Because refining techniques generally'usedinthe'processing-of'cr ude petroleum oil fractions are limited in theirability to-produce gasolines of high F-Z antiknock quality, thesensitivity of gasolines produced in thismanuer has increasedappreciably since the advent of these processes. An important reason forthe liability of the more sensitive fuels is theincreased use ofautomatic, automotive transmissions which raise the speed of maximumoctane requirement. The trend toward motor fuels of increased sensiicein composition, formance.

According to this invention, it has been found that the octane numbercharacteristics of a gasoline of this nature can be improved byfractionating the gasoline to obtain a low-boiling fraction and ahigh-boiling fraction. The low-boiling fraction is mildly hydrogenatedand the highboiling fraction is reformed in the presence of a noblemetal catalyst. By blending the treated fractions a fullboiling-rmgegasoline having a high octane level and a low sensitivity is prepared.In thefigure is shown a processing sche for carrying outlthis invention.A gasoil feed stock, obtained from a suitable source not shown, isintroduced through line 10 into a conventional catalytic crackingprocess 11. The reaction effluent from the cracking process istransferred through line 12 to fractionator 13 where it is separatedinto an unstabilized gastivity is due primarily to the significantposition of catalytic cracking processes in the refiners scheme ofoperations.

, The formula for finished high-octane-number gasolines includes as themajor constituent a full-boiling-range gasoline produced in aconventional catalytic cracking process such as F.C.C-., T.C.C., Houdryprocess or the like. Blended' with this base fuel are a number of otherblending components such as gasoline fractions produced byreformingpolymeriZation, alkylation, isomerization, etc,

of specially selected fractions. .It is therefore essential treatment ofa gasoline manufactured in a fluid catalytic cracking process to producea high-octane gasoline.

These and other objects will be made apparent from the followingdetailed description of this invention.

In the figure is shown schematicallya processing'fiow diagram of therefinin process of thisinvention;

The key refinin process in the production of high octance gasolines iscatalytic cracking wherein I gasjoil streams from atmosphericdistillation, vacuum distillat on,

and bottoms-processing units are treated togive a high yield of ahigh-grade gasoline. Catalytic cracking processes which arecomprehensively described in the prior art are categorized as threedifferent types, viz., fixed bed, e.g., Houdry; moving bed, e.g.,T.C.C.; and fluid systems, e.g., F.C.C. For given conditions ofoperation and cataly'st compositions, the chemistry of these processescan be considered essentially the same, involving C-C scission, 1.

'aromatization, isomerization, and polymerization. For

this reason, as pointed out in Progress in Petroleum, Ad-

vances in Chemistry'Se'ries' #5, A.C.S., 1951 at page 12,

the gasolines produced in the catalytic cracking of a wide variety ofpetroleum feed stocks have notable'similarities oline cut, and otherfractions boiling above the gasoline range. The gasoline cut'is passedvia line 14 to second fractionator 15 where it is stabilized,anclfractionated into a low-boiling fraction and a high-boilingfraction. 'The lower-boiling fraction is withdrawn from fractionator 15through line 16 and processed in hydrogenation unit 17. Thehigher-boiling fraction leaves fractionator 15 and is sent to reforming:unit 18 through line 19. Therea'ction efiiuent leaving hydrogenationunit 17 ,iseondens'ed and the liquid product transferred through line20. 1Similarlythe liquid reformate from reforming 'unit 18 passesthrough line 21 to a point of confluence with line 20. The

respective streams are blended in-line 22 to produce a gasoline producthaving a high F-l octane numberand a low sensitivity.

In the treatment of a variety of gasoline's obtained in the catalyticcracking of suitable petroleumfraction's the basic split treatmenttechnique outlined above can be effectively employed. For practicalreasons, however, it is preferred that the high-boiling fraction behydrofined prior to reforming by means of a conventional guardcaseoperation (World Petroleum 26 (2), 44-6). By pretreating thisfraction in'this manner, better temperature control during reforming isobtained because the hydrogenation reaction, which is generallyaconcornitant action during the reforming, is exothermic. Furthermore,reforming catalysts employed in this invention are sensitive' to sulfur.Therefore by pre-hydrofining the highboiling fraction, the sulfurcontent of this fraction issu'bstantially reduced and catalyst poisoningmitigated. In commercial reforming operations, pre-hydrofining of thefeed stock is effected by having a guard case ahead of the reformer inthe process scheme. The pre-hydrofining of this fraction,if employed, iscarried out under the same conditions which are employed'in mildlyhydfogehating the low-boiling fraction. Accordingly an alternativeprocessing scheme would involve the hydrogen treating of thefull-boiling-range gasoline obtained from a catalytic cracking processfollowed by the abovedescribed, basic, split-treatment technique. 7

To further illustrate the invention, a gasolinewas produced in the fluidcatalytic cracking of 21 Mid-Continent gas-oil having the followingcharacteristics:

API' gravity 27.2 Boiling range I IBP 10% t 5 55 50% 733 v 70% e 812E.-P. 1000 Sulfur, t. percent 0.55 Carbon'residue; percent wt. 0.30

Aniline point, 0 F. t via, sus, F.

physical properties, and engine per-Q Reaction pressure p ig 16 Spacevelocity, v./hr./v. 4 Conversion percent 55 The stabilized gasolineproduced was fractionated into consecutive fractions consisting of alow-boiling fraction and a high-boiling fraction, having thecharacteristics tabularly summarized in Table I:

TABLE I Inspection data for light and heavy fractions of gasolineFraction Full- Low- High- Boillng- Bolling- Boiling- Range FractionFraction Gasoline Vol. Percent of Debutanized Gaso 41. 9 58. 1 Gravity,API 58. 79. 9 45. 2 ASTM Distillation, F.:

IBP 98 210 106 227 108 237 110 247 112 257 115 271 119 290 123 314 128337 136 356 146 383 152 401 158 159 426 99.8 98. 7 0. 2 1.1 Loss 1. 20.0 0. 2 Reflective Index, n lD 1, 4215 1, 3810 1. 4505 Vol. PercentNaphthenes and Parafins. 41.1 41. 3 35.3 Vol. Percent Olefins 38. 3 57.3 27. 8 Vol. Percent Aromatics--- 20.6 1. 4 36. 9 Total Sulfur, WtPercent 0.081 0.018 0.12 Research Octane, Clear 94. 0 96. 0 90. 7 .Oml.T +0.10 95. 4 Motor Octane. Clean- 81. 2 81.0 80.0 +8.0 ml. TEL 88.0 83.8

The low-boiling fraction was hydrogenated in a 1" stainless steelreactor in which the top section contained the preheater. The reactorfits in a bronze block maintained at the operating temperature. Thehydrogenation was carried out under mild operating conditions employing9% molybdenum oxide on alumina as the hydrogenation catalyst (FiltrolR-.-3241). This operation is summarized in Table II.

. TABLE [I Hydrogenation of low boiling gasoline fraction0peratingconditions and results Operating conditions:

Temperature, F. 625 Pressure, p.s.i.g 500 LVHSV 2.5 H rate, ftfi/bbl.(STP) 1821 Material balance, percent 99.2

No-loss liquid recovery:

Wt. percent of liq. charge 99.7

Vol. percent of liq. charge 102.0

,The characteristics of the hydrogenated product are listed in TableIII:

4 TABLE III-Continued 70% 128 136 147 95% 156 DR 169 E.P. 171 Rec. 97.9Res. 0.8

, Loss 1.3 Refractive index, n /D 1.3680 Vol. percent naphthenes andparafiins 99.0 Vol. percent olefins 0.2 Vol. percent aromatics 0.8 Totalsulfur, wt. percent 0.003 Research octane, clear 79.9 +3.0 ml. TEL 95.6Motor octane, clear 81.4 +3.0 ml. TEL 97.1

The high-boiling fraction was'catalytically reformed in the presence ofa (Sinclair-Baker RD-ISO) silicaalumina-platinum catalyst at a reactorinlet temperature of 1000 F., 500 p.s.i.g. pressure, liquid volumehourly space velocity of 1.6 and a hydrogen rate equivalent to 2850ftfi/bbl. The feed stock was pre-hydrofined m-a guard case which wasoperated under the following conditions, employing a catalyst consistingof 9% molybdenum oxide on alumina (Filtrol R-3241):

Temperature, F. 700 Pressure, p.s.i.g. 500 'LVHSV 2.5 H rate, ftfi/bbl.(STP) 2000 The characteristics of the finished product are listed inTable IV:

TABLE IV Catalytic reforming of hydrogenated heavy F.C.C.gasoline-Inspection data for liquid product Gravity, API 42.6 ASTMdistillation, F.:

I.B.P. 82 5% 116 10% 139 20% 193 30% 237 40% 264 50% 280 60% 295 70% 312334 400 E.P. 501 Rec. 94.9 Res. 1.1 Loss 4.0 Refractive index, n /D1.4642 V01. percent naphthenes and paraffins 26.0 Vol. percent olefins0.9 Vol. percent aromatics 73.1 Wt. percent total sulfur 0.021 Vol.percent C s and lighter 2.0 Vol. percent C s 7.3 Vol. percent C s andheavier 90.7 Molecular wt. (C s+) Specific gravity (C s+) 0.8338Research octane, clear 102.7 Research octane, +3 m1. TEL 105.8

The hydrogenated fraction and catalytically, reformed fraction wereblended to provide a full-boiling-range gasoline. In order todemonstrate the uniqueness of the processing steps of this invention,several other techniques were investigated. The comparative results areshown in Table V,

, TABLE V Inspection data on finished gasoline blends L.-B. GasolineHydrogenated Hydrogenated Low-Boiling L .-B. Gasoline +405 F. EP Hydro-L.-B. Gasoline L.-B. Gasoline Gasoline+ +Catalytically Thermallygenerated +Catalytically +405 F. EP Gasoline Blend High-Bolling ReformedHy- Reformed L.-B. Gaso- Reformed Thermally Gasoline drogenatedHydrogenated line +H.-B. Hydrogenated Reformed H.-B. Gasoline H.-B.Gasoline Gasoline H.-B. Gasoline Hydrogenated V H.-B. Gasoline ReformingRun N OR-9 TC-8 CR-9 '10-8 Yield of Finished Gasoli a Per 100.0 89.789.8 100.8 90.5 90.6 Gravity, API (Oalcul 58. 3 58. 2 60. 6 60.1 60. 362. 6 Refractive Index, 'n /D 1.4220 1.4264 1.4178 1. 4160 1.42001;.4'105' Vol. Percent Naphth v Parafiins 38.4 33.6 43.4 63.8 61.3 697Vol. Percent Oleflns... 39.7 24.2 32.5 15.3 0.2 8.2

It is evident that the foregoing illustrative example isnon-limiting andthat other manipulative techniques can be employed in carrying out thisinvention. In selecting the cut-point for separating the low-boilingfraction and high-boiling fraction, the proportion of thefull-boilingrange gasoline which is to lie-hydrogenated is determinedexperimentally. The selected low-boiling fraction will be is notdesired,jthe process can be carried out without fraction, provides afull-boiling-range gasoline having a H maximum appreciation in motoroctane number (F-2) with a minimum depreciation in research octanenumber- (F-I Generally, the low-boiling fraction will have an ASTMend-point of about 175 'F.; however, this may vary from about 150-to 250F. The importance of empirically ascertaining the cut-point isillustrated by fractionating a full-boiling-range gasoline, obtainedfrom the fluid catalytic cracking of a gas-oil, to provide the threelow-boiling fractions, (1) I.B.P.150, (2) I.B.P.'-- 175, (3)I.B.P.--200, described in Table VI. These re- .spective fractions wereprocessed employing, as a hydrogenation catalyst, a composite comprisingasilicaalumina support having incorporated therein 5%nickel, butmolybdena on alumina or any other hydrogenation catalyst may be used.The effect of boiling range on reducing the sensitivity of the blendscontaining the varicos hydrogenatedfractions is shown in Tables VII andVIII. These tables show respectively the operating conditions andresults obtained, and a comparison of the efiect of hydrogenating thevarious fractions on the fullboiling-range gasoline after blending backeach fraction. In the event that maximum octane number improvementreforming the higher-boiling fraction, and thus provide principallyanenhancement in the sensitivity of the gasoline. 1 TABLE VI Inspectiondata Fraction IBP- IBP-I- IBP-'-.' 150 F. 175 F. 200 F.-

Vol. percent of 350 F. EP FCC Gaso; 33. 5 50.8 60. 8 Gravity, API 87. 882.0 78.1 ASTM Dist F I'BP 87 96 101 104 109 91 105 no 92 107 1 1 5 93109 118 94- 112 123 95 128 96 119 98 125 101 134 158 108 146 176 118 153190 132 p 137 163 v203 98. 2 98; 5 985 4 0. 4 0. 8 0.8 Loss 1. 4 0.7 0.8 Refractive Index, n /D 1 8680 1. 3775 1. 3830 Vol. percent Naphthenesand Parraffins 53. 1 50. 9 49. 6 Vol. percent Olcfins 46. 9 48.0 482Vol. percent Aromatics" 0.0 1. 1- 2. 2 '12. percent Su1fur 0.014 0.0100.017 F-l Octane, Clear 102. 8 101.0 100.4 F-2 Octane, Clear I 89. 0 87.2 88.0

These octane ratings were calculated after blending with 50% 80/20octane reference fuel and determining the octane, rating of the; blend.Because of the difficulty of running the verylow-boiling materialstraigh it was blended with the heavier reference fuel.

TABLE VII Reducing the sensitivity of low-boiling fraction gasoline'- IOperating conditions and results Fraction IBP F. IBP F. IBP"200 I.

Catalyst 5% Ni on 5% Ni on 5% Ni on= S102-A1203. slot-41.0.. SlOr-AlrOn.

Temperatur 602 57 552. Pressure, P s I g 500 500. LVHSV- 1.7-. 1.0. H:Rate, Ftfi/bbl. (STP)- V 2036 V 3481. Material Balance, Percent. 99.9101.5. No-Loss Wt. Percent Liquid Rec 97. 98.0. No-Loss ,Vol. PercentLiquid Rec 98. 98.9. Liquid Product Inspection;

Gravity, APL. 89. 79.8.

Refractive Index, 118 /13-. 1.36 1.3761.

F-l Octane, Clear a 87.4 80.6.

F-2 Octane, Clear I 82.3 80.0.

Sensitivity 5.1. 0.6.

Vol. Percent Naphthenes-i-Parafiins- 100. 97.8.

Vol. Percent Olefins- 0.0- 0.4.

Vol. Percent Ar a 0.0 1.8.

Total Sulfur, Wt. P w-Put I Theseoct'ane ratings were calculated afterblendingwith 50% 80/20 octane reierericeduel and determining the octanerating of the blend.

TABLE vm of 350 F .E.P. gasolines Fraction Hydrogenated None IBP-150 F.IBP-175" F. IBP200 1".

Run Nn H-7 H-8 H9. Catalyst- 5% Ni on 5% Ni on 5% Ni on Slog-A1203.SiOzA120: SlOr-AhOp Vol. Percent Hydr as s 50.8. 60.8. Vol. Percent 'sand Heavier, EP Gasoline 1000--.. 0 M 6 100.6 Gravity API 61. 62 6 62.4.Aniline some 100.9 104.7. ASTM Distillation, F

IBP m2 as 99 100, 5 7 11s 1m its 119, 10 124 125 125 127. 1'16 137 137138. 147 151 152 152. 164 17 17 173. 50 187 195 199 202. 60 216 994 233237. 70"- 254 256 265 267. 80" 288 286 293 298. 90 315 320 327. 05"'-335 2'40 335 346. D] 3 348 36 378. EP 360 354 369 386. Rec- 97.8--- 98 998 6 98.1. Res. 0.0 0.9 1.0 0.9. Tnu .2 1.0. ASTM G t 2 InductionPeriod, Mins 1155. Reid Vapor Pressure. 8.0. Reflective Index, ri /D1.4105. Vol. Percent Naphthenes+Paraifins 71.4. Vol. Percent Olefins8.9. Vol Percent Aromatics 19.7. Total Sultur, Wt. Percent.. 0.031. F-lOctane, Clear 86.3. F-l Octane, +3 cc. TEL. 97.3. F-2 Octane, Clear80.1. F-2 Octane, +3 ce. TEL (Cal 91.1. Sensitivity 6.2.

To effect the hydrogenation of the selected lowboiling fraction, or thepre-hydrofining of the high-boiling fraction, conventional techniquesare used. Operating conditions which can be employed are as follows:

1 Liquid volume hourly space velocity.

The catalyst employed in these hydrogenation steps is one commonly usedin a hydrogenation reaction involving hydrocarbon feed stocks.Preferably oxides and salts of, or elemental, group VI or VIII metals,either alone or supported on a suitable carrier such as silicaalumina,alumina, kieselguhr, etc., are used, including but not limited tonickel, platinum, copper chromite, sulfides and oxides of nickel,molybdena, cobalt, tungsten and others. A preferred catalyst for thispurpose is a molybdena-on-alumina catalyst described in our copendingapplication SerialNumber 593,821, filed June 26, 1956.

In a similar manner, the catalytic reforming of the higher-boilingfraction employs customary processes utilizing group VIII noble metalcatalysts comprising platinum or palladium deposited on a suitablesiliceous carrier. A number of compositions of this nature are describedin the patent art. For example, see US. Patents 2,479,109; 2,478,916;2,550,531; 2,589,189; 2,750,329 and others. It is preferred in carryingout the reforming phase of this invention to employ a platinum catalystcontaining 0.2 to 0.6% platinum on ahigh-area alumina having a surfacein excess of 350 square meters per gram. The catalyst maybe in theextruded form having diameters of The reforming operation carried out inaccordance with this invention is conducted at temperatures in the rangeof 900 to 1050 F., and pressures of about 300 to 600 p.s.i.g. A- liquidvolume hourly spacevelocity 0f 1 to 3 can be used with a molar ratio ofhydrogen/hydrocarbon feed of 1 to 6: 1.

The catalytic gasoline to be upgraded may be produced by any know methodusing static bed reactors, moving bed reactors or fluidized bedreactors. The charge stock should contain at least 50% virgin materialbut may contain a minor amount of recycle or extraneous material. Theboiling range of the charge should run from about 450 F. up to 1000 F.or more. The catalyst employed may be either a natural or syntheticcracking catalyst and may be in powdered, granular, or speciallymanufactured forms. Conventional catalytic cracking conditions employingtemperatures of about 900 to 1000 F. and conditions to provide 50 to 60%conversions are used.

From the foregoing data, it is seen-that by means of the integratedhydrogenation-reforming process of this invention a gasoline from acatalytic cracking process can be upgraded to produce a high octanenumber product with decreased sensitivity. If the full-boiling-rangegasoline is hydrogenated, there is a loss in both the motor octanenumber (F-2) and research octane number (F-l). It has been found thatwhile gasolines from catalytic cracking processes are receptive totreatment in accordance with this invention, gasolines obtained fromthermal cracking do not similarly respond. For example, in mildlyhydrogenating a low-boiling gasoline fraction having an ASTM boilingrange of I.B.P.-l F., produced by the thermal cracking of a gas-oil feedstock, there was experienced a decrease in sensitivity; however, therewas a depreciation in both the motor octane number (E2) and the researchoctane number (F-l). Therefore, this invention is limited in accordancewith the process details set forth in the appended claims. It isevident, however, that various modifications of the described processcan be made by those skilled in the art without departing from the scopeof this invention.

We claim:

1. A process for enhancing the octane number and improving thesensitivity of full-boiling range leaded gasoline produced in thecatalytic cracking of petroleum gas oil comprising separating from saidgasoline a plurality of consecutive higherand lower-boiling fractionpairs, said lower-boiling fractions having end-boiling points difieringsubstantially from each other and ranging from about 150 to 250 F.,catalytically hydrogenating each of said lower-boiling fractions bycontacting with hydrogen in the presence of a hydrogenation catalystselected from the group consisting of nickel on silicaalumina supportand molybdena on alumina support, at a temperature in the range of about550 to 700 F., a pressure in the range of about 350 to 500 p.s.i., aliquid volume hourly space velocity in the range of 1-5, and a hydrogenrate in the range of 1000.3 000 cubic feet per barrel, blending eachhydrogenated fraction back with the higher boiling fraction from whichit was separated and with the desired amount of tetraethyl lead,determining the sensitivity of the resulting blend in each case andthereafter catalytically hydrogenating under the aforesaid hydrogenatingconditions that fraction of the gasoline corresponding to the samplewhich gave the lowest sensitivity without substantial decrease inresearch octane number of the blend, catalytically hydroforming thehigher boiling fraction of the gasoline and blending the resultinghydrogenated fraction with the higher boiling hydroformed fraction toobtain a full boiling range gasoline of high octane number and lowsensitivity.

2. Method in accordance with claim 1 in which i 10 hydrogenation iscarried out at a temperature of about 550-600 F., pressure of about 500lb./sq. inch, liquid hourly space velocity of about 1.0-2.2 and hydrogenrate of about 1500-3000 cubic feet per barrel of gasoline fractioncharged.

3. Process in accordance with claim 1 in which the fraction subjected tomild hydrogenation has an ASTM end point of about 175 F.

4. A process in accordance with claim 2 in which hydrogenation iscarried out in the presence of a catalyst comprising a major portion ofalumina and a minor amount of molybdena.

5. A process in accordance with claim 4 in which said higher-boilingfraction is hydroformed at a temperature of 900-1050 F., a pressure of300-600 p.s.i.'g., a liquid volume hourly space velocity of 1-3, and amolar ratio of hydrogen to hydrocarbon feed of 6-1:].

References Cited in the file of this patent UNITED STATES PATENTS2,436,170 Hill Feb. 17, 1948 2,463,741 Byrns Mar. 8, 1949 2,740,751Haensel et a1. Apr. 3, 1956 2,810,004 Morbeck et a1 Oct. 15, 1957

1. A PROCESS FOR ENHANCING THE OCTANE NUMBER AND IMPROVING THESENSITIVITY OF FULL-BOILING RANGE LEADED GASOLINE PRODUCED IN THECATALYTIC CRACKING OF PETROLEUM GAS OIL COMPRISING SEPARATING FROM SAIDGASOLINE A PLURALITY OF CONSECUTIVE HIGHER- AND LOWER-BOILING FRACTIONPAIRS, SAID LOWER-BOILING FRACTIONS HAVING END-BOILING POINTS DIFFERINGSUBSTANTIALLY FROM EACH OTHER AND RANGING FROM ABOUT 150* TO 250*F.,CATALYTICALLY HYDROGENATING EACH OF SAID LOWER-BOILING FRACTIONS BYCONTACTING WITH HYDROGEN IN THE PRESENCE OF A HYDROGENATION CATALYSTSELECTED FROM THE GROUP CONSISTING OF NICKEL ON SILICAALUMINA SUPPORTAND MOLYBDENA ON ALUMINA SUPPORT, AT A TEMPERATURE IN THE RANGE ABOUT550* TO 700*F., A PRESSURE IN THE RANGE OF ABOUT 350 TO 500 P.S.I., ALIQUID VOLUME HOURLY SPACE VELOCITY IN THE RANGE OF 1-5, AND A HYDROGENRATE IN THE RANGE OF 100-3000 CUBIC FEET PER BARREL, BLENDING EACHHYDROGENATED FRACTION BACK WITH THE HIGHER BOILING FRACTION FROM WHICHIT WAS SEPARATED AND WITH THE DESIRED AMOUNT OF TETRAETHYL LEAD,DETERMINING THE SENSITIVITY OF THE RESULTING BLEND IN EACH CASE ANDTHEREAFTER CATALYTICALLY HYDROGENATING UNDER THE AFORESAID HYDROGENATINGCONDITIONS THAT FRACTION OF THE GASOLINE CORRESPONDING TO THE SAMPLEWHICH GAVE THE LOWEST SENSITIVITY WITHOUT SUBSTANTIAL DECREASE INRESEARCH OCTANE NUMBER OF THE BLEND, CATALYTICALLY HYDROFORMING THEHIGHER BOILING FRACTION OF THE GASOLINE AND BLENDING THE RESULTINGHYDROGENATED FRACTION WITH THE HIGHER BOILING HYDROFORMED FRACTION TOOBTAIN A FULL BOILING RANGE GASOLINE OF HIGH OCTANE NUMBER AND LOWSENSITIVITY.